Thermodynamic limitations on the use of the platinum electrode in <i>Eh</i> measurements

Abstract

The thermodynamic stability of surface oxide and sulfide coatings on the platinum electrode is considered. In well mixed environments thermodynamic considerations and experimental evidence suggest that the platinum surface acts as an oxide electrode that responds to pH rather than to oxygen partial pressure. In stagnant conditions in the marine or estuarine environment the slow formation of platinum sulfide may push the measured Eh values to more negative potentials if permanently emplaced electrodes are used. These reactions may restrict the operational use of Eh measurements.